Distribution of Gefitinib to the Brain Is Limited by P-glycoprotein (ABCB1) and Breast Cancer Resistance Protein (ABCG2)-Mediated Active Efflux

Abstract

Gefitinib is an orally active inhibitor of the epidermal growth factor receptor approved for use in patients with locally advanced or metastatic non-small cell lung cancer. It has also been evaluated in several clinical trials for treatment of brain tumors such as high-grade glioma. In this study, we investigated the influence of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) on distribution of gefitinib to the central nervous system. In vitro studies conducted in MadinDarby canine kidney II cells indicate that both P-gp and BCRP effectively transport gefitinib, limiting its intracellular accumulation. In vivo studies demonstrated that transport of gefitinib across the blood-brain barrier (BBB) is significantly limited. Steady-state brain-to-plasma (B/P) concentration ratios were 70-fold higher in the Mdr1a/b(Ϫ/Ϫ) Bcrp1(Ϫ/Ϫ) mice (ratio of approximately 7) compared with wild-type mice (ratio of approximately 0.1). The B/P ratio after oral administration increased significantly when gefitinib was coadministered with the dual P-gp and BCRP inhibitor elacridar. We investigated the integrity of tight junctions in the Mdr1a/b(Ϫ/Ϫ) Bcrp1(Ϫ/Ϫ) mice and found no difference in the brain inulin and sucrose space between the wild-type and Mdr1a/b(Ϫ/Ϫ) Bcrp1(Ϫ/Ϫ) mice. This suggested that the dramatic enhancement in the brain distribution of gefitinib is not due to a leakier BBB in these mice. These results show that brain distribution of gefitinib is restricted due to active efflux by P-gp and BCRP. This finding is of clinical significance for therapy in brain tumors such as glioma, where concurrent administration of a dual inhibitor such as elacridar can increase delivery and thus enhance efficacy of gefitinib.Malignant gliomas account for approximately 70% of all new cases of malignant primary brain tumors diagnosed in the United States every year. Glioblastoma multiforme (GBM) is the most common type of glioma, accounting for approximately 60 to 70% of malignant gliomas (Wen and Kesari, 2008; CBTRUS, 2008) and claiming 12,000 lives every year (Davis et al., 2001). Epidermal growth factor receptor (EGFR) and its variant EGFRvIII play a critical role in the development of an aggressive phenotype of GBM; EGFR amplification, mutation, and overexpression are associated with poor prognosis and resistance to therapy (Brandes et al., 2008). Several therapeutic strategies targeting EGFR in GBM have been proposed, including the use of monoclonal antibodies against EGFR or EGFRvIII, vaccine therapies, bispecific antibodies, toxin-linked conjugates, and small molecule tyrosine kinase inhibitors (Omuro et al., 2007).

Quantitative Proteomics of Transporter Expression in Brain Capillary Endothelial Cells Isolated from P-Glycoprotein (P-gp), Breast Cancer Resistance Protein (Bcrp), and P-gp/Bcrp Knockout Mice

“…This was first reported by de Vries et al (2007) and Polli et al (2009), who showed that P-gp and Bcrp work together to modulate the CNS penetration of topotecan (de Vries et al, 2007) and lapatinib (Polli et al, 2009), respectively. Furthermore, in our previous studies in Bcrp, P-gp, and P-gp/Bcrp knockout mice, we reported similar findings with dasatinib (Chen et al, 2009), gefitinib (Agarwal et al, 2010), and sorafenib (Agarwal et al, 2011b). These results showed that brain penetration of dual substrates increased disproportionally in the absence of both P-gp and Bcrp at the BBB.…”

“…Brain distribution studies using these mice have shown that many drugs have limited CNS distribution due to P-gp-and/or Bcrp-mediated efflux (Lee et al, 2005;de Vries et al, 2007;Polli et al, 2009;Agarwal et al, 2010Agarwal et al, , 2011bKodaira et al, 2010;Tang et al, 2012). However, the finding that brain distribution of several dual P-gp and Bcrp substrates increased remarkably in mice deficient in both P-gp and Bcrp was unexpected, because there was no dramatic increase in their brain penetration in the single P-gp-or Bcrp-deficient mice.…”

“…However, the finding that brain distribution of several dual P-gp and Bcrp substrates increased remarkably in mice deficient in both P-gp and Bcrp was unexpected, because there was no dramatic increase in their brain penetration in the single P-gp-or Bcrp-deficient mice. This has now been reported for several drugs that are substrates for both P-gp and Bcrp (de Vries et al, 2007;Polli et al, 2009;Agarwal et al, 2010;Kodaira et al, 2010). Whereas studies have tried to explain this cooperation of P-gp and Bcrp at the BBB using simple quantitative models with several assumptions (Kodaira et al, 2010), the exact mechanism of this synergistic/cooperative effect is still unclear.…”

“…Although some of these questions pertain to the integrity of the BBB in these mice (Agarwal et al, 2010), the major question is whether genetic modification of one transporter causes changes in regulation and/or expression (up or down) of other critical transporter proteins that may influence their functional role in drug disposition to the brain. Certainly, up-regulation of P-gp in the Bcrp1(Ϫ/Ϫ) mice could, in part, explain why brain penetration of dual substrates is not enhanced in these mice.…”

Inhibition of ABCB1 Overcomes Cancer Stem Cell–like Properties and Acquired Resistance to MET Inhibitors in Non–Small Cell Lung Cancer

“…Elacridar inhibited ABCG2 as well as ABCB1 and has been used in preclinical and clinical settings (38,39). Elacridar can also significantly increase plasma pharmacokinetics and brain distribution of several drugs, including dasatinib (40), gefitinib (41), and sunitinib (42). In this study, ABCB1 knockdown reduced the numbers of oncospheres and suppressed EMT features in EBC-1R cells.…”